Extension of our studies to related forms of mercury is a logical and necessary development of the present program on methylmercury. The real hazard to human health cannot be properly estimated without considering possible additive and synergistic effects of multiple exposures to different forms of mercury viz. daily exposures to phenylmercury in contraceptive and cosmetic preparations and occupational exposure to metallic vapor. The studies on metallic vapor and the phenylmercurials will call heavily on methods and procedures already established for methylmercury.